1. Field of the Invention
The present invention relates to a portable shelter whose frame members expand and contract between maximum and minimum dimensions. This movement permits selectively applying various sized shelter skins to a single frame and provides flexible resistance to the forces of the wind against the portable shelter skin. Such structure also provides a means for tensioning the shelter skin to keep the skin taunt against the frame when wind forces are not present.
2. Description of the Prior Art
Portable shelters are well known in the art and include various structures from simple pup tents to larger and more complex shelters, for example circus tents. These portable shelters are constructed using frames that are generally rigid in the belief that rigidity is necessary to resist the forces of the wind against the shelter skin. Adjustability built into most portable shelters is primarily to ease assembly and to provide some limited stretching of the shelter skin. In many cases, the shelter skin extends from the shelter poles without structural support, being simply stretched as taunt as possible in order to maintain the interior space. Without structural support the shelter skin flaps and moves with the wind creating a collapsing and expanding interior space frequently to the discomfort of those occupying the shelter. In addition, strong winds striking shelters supported by rigid frames such as that disclosed by U.S. Pat. No. 2,897,831 issued to O. G. A. Liden, meet such resistance and lack of flexibility that the structures may collapse.
The current art requires that when portable shelters of different sizes are needed a new shelter must be obtained, including a new frame and a new skin. Another problem with proper fit occurs when shelter skins shrink in some areas and stretch in others so that they no longer properly fit frames that have fixed dimensions.
Notwithstanding the existence of such prior art, it remains clear that there is a need for a portable shelter having a frame that provides full support for a shelter skin in order to maintain the interior space and yet provides flexibility so that the portable shelter can flex and give in strong winds. There is a need for a portable shelter having a frame that provides structure for tightening the skin in relation to the frame to reduce the amount of flapping of the skin and to reduce sagging of the skin into the interior space. There is also a need for a frame that may be enlarged by extending the existing members of the frame or by adding new members, which only requires the purchase and storage of a larger skin.